A field chopper generally comprises a vehicle chassis or frame which may be towed by a tractor or self-propelled and which carries a blade drum or reel rotatable about a horizontal axis and driven by the power take-off of the tractor or a prime mover carried on the chassis or frame.
At the front end of the field chopper, a head is provided depending upon the nature of the crop material to be processed. For example, if a mown or swath crop is to be harvested, the pickup head may comprise an apron, conveyor or pickup drum to lift the mowed crop material from the ground and carry it toward the blade drum. If a standing crop is to be harvested, the apron or leading edge of the field chopper may be provided with a sickle bar or the like for simultaneously mowing the crop. When corn or another row crop is to be harvested, the head generally comprises guide shoes forming a throat into which the upright stalks are guided and chains or the like for engagement with these stalks to carry them toward the cutter drum in the proper orientation for subdivision. Means may be provided for severing the stalks just above the ground level.
The field chopper may also comprise a blower for displacing the comminuted material into a forage wagon or other conveyance which may be drawn along the field chopper and with means between the crop intake head and the cutter drum for advancing the crop material toward the latter.
The crop-advancing means can comprise, for example, a plurality of lower rollers over which the crop material is guided and respective pressing rollers which bear downwardly upon the crop material and press it against the lower rollers. Such rollers may be driven.
In the field chopper described in German Pat. No. 966,671, (corresponding to U.S. Pat. No. 2,747,634)system of the character described above, and are driven by a chain running over sprocket wheels connected to the pressing-roller shafts. In this construction it has been found that the chain drive is susceptible to damage and contamination and is of relatively expensive construction.
An especially important disadvantage of this system is that the chain drive makes the cutter drum and any counter blades on the vehicle chassis accessible only with difficulty. Frequently access to the cutter drum and the fixed blade or surface with which it cooperates must be made available for clearing jams, repairing damage or the like. Chain-drive systems of the aforementioned type are difficult to disassemble and make it particularly inconvenient to remove the pressing roller lying immediately ahead of the blade drum. The removal of such rollers is frequently necessary for convenient access to the blade drum.